This invention relates to an improved method and apparatus for the pyrolysis of carbonaceous materials in a rotary kiln wherein at least a portion of the thermal energy required for pyrolysis is provided by the in situ combustion of at least a portion of the pyrolysis gases. More particularly, it relates to an improved method and apparatus for supplying and distributing an oxygen-containing gas at the burner end of a direct-fired rotary kiln for the support of such in situ combustion of the pyrolysis gases.